This is really excellent so far. You're a pro at writing scenarios that immerse the players. The only thing you have trouble with is dialogue, and I used to make these tiny mistakes all the time (still do sometimes), so I'm just lending some minor advice.
You try to pass some time, but get bored quite quickly, so you decide to ask about what to do now from Marcus. "I don't know. Do whatever you want, I'll tell you about your next assignment tomorrow when all have returned." He replies to your question. That didn't leave you satisfied at all.
Narrative around dialogue can be confusing, but generally stating an action related to dialogue is best made before the dialogue itself, like this.
He replies to your question: "I don't know. Do whatever you want, I'll tell you about your next assignment tomorrow when all have returned."
Since the narrative sentence is only six words you can get away with a colon. Otherwise it's a comma, like I'll demonstrate here:
He immediately notices you and yells " Assassin!"
Instead, it would be
He immediately notices you and yells, "Assassin!"
Of course, you could have used a colon there, too, as commas are generally optional when the pre-dialogue narratives are 6 words or less. Nobody's anal about that, though. Additionally, since the dialogue ends in punctuation, you can get away with the next word starting a sentence.
He immediately notices you and yells, "Assassin!" He then aims at you with his bow and shoots,
These aren't gripes, just interesting advice. I struggle with dialogue myself. Clearing out (obvious) grammar mistakes can make a good turn just a little better.